meta: improve documentation, add testing workflow

.github/workflows/rust.yml

@@ -0,0 +1,21 @@
+name: Rust
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Build
+        run: cargo build --verbose
+      - name: Run tests
+        run: cargo test --verbose

README.md

@@ -8,6 +8,73 @@ This project aims to close the gap between features offered for each platform. S
 
 We hope GOG will eventually provide that data themselves, untill then we are on our own.
 
+## API
+
+Currently supported enpoint returns game config from `remote-config.gog.com` endpoint. If there is Linux data in games_data directory that will be extended
+
+```
+GET /api/config/client_id
+```
+
 ## Contributing
 
-The `games_data/` directory contains `ClientId.json` files for each game. Contributions to that directory are welcome. All json files are formatted using Prettier
+The `games_data/` directory contains `ClientId.json` files for each game. Contributions to that directory are welcome. All json files are formatted using Prettier.
+
+### Obtaining the relevant game data
+
+Let's say, you want to add a new linux native game to suport cloud saves.
+
+1. Go to https://gogdb.org
+2. Find the game package you want to add
+3. Pick a game build (eg. https://www.gogdb.org/product/1308320804/build/54853937123913458)
+4. Copy client id
+5. Make a [request to the API](#api) with it
+6. Find corresponding paths on Linux
+7. Write config file
+
+### Sample config
+
+```json
+{
+  "overlay": { "supported": false },
+  "cloudStorage": {
+    "enabled": true,
+    "locations": [
+      {
+        "name": "saves",
+        "location": "<?XDG_CONFIG_HOME?>/unity3d/Team Cherry/Hollow Knight",
+        "wildcard": "*.dat" // This can be null
+      }
+    ]
+  }
+}
+```
+
+- overlay - not used currently, enabled should be set to false for now
+
+- cloudStorage - enabled field indicates whether cloud saves are supported; locations is a array of objects containing name, location and wildcard
+
+- name - location name - this should be set to same value as on Mac or Windows
+
+- location - place where files are stored - this can use env vars like `$HOME`, values that have fallbacks (like `$XDG_CONFIG_HOME` falls back to `$HOME/.config`) should be closed in `<?SOME_VAR?>`
+
+- wildcard - value can be set to `null`. Due to nature of some games on Linux that's required to not push unrelated junk to the cloud (that's usually a case for Unity games)
+
+**IMPORTANT NOTE**  
+Some games can have enabled `cloudStorage` but empty locations array. This is caused by the fact that such games use `__default` location which is only available on Windows and Mac, since it's handled by Galaxy SDK (which doesn't exist on Linux btw). [SDK Documentation related to this](https://docs.gog.com/sdk-storage/#cloud-saves)
+
+In that case config should still be defined if it's compatible, however the name should be set to `__default`
+
+### Common location vars
+
+Used on Windows and Mac
+
+```
+INSTALL
+SAVED_GAMES
+APPLICATION_DATA_LOCAL
+APPLICATION_DATA_LOCAL_LOW
+APPLICATION_DATA_ROAMING
+APPLICATION_SUPPORT
+DOCUMENTS
+```